package stack_queue.leetcode;
import java.util.Stack;
public class Num232 {
    /**
     * 双栈模拟队列
     **/
    public class MyQueue {
        // 实际存储元素的栈
        private Stack<Integer> s1 = new Stack<>();
        // 辅助栈
        private Stack<Integer> s2 = new Stack<>();

        public MyQueue() {

        }

        public void push(int x) {
            if (s1.isEmpty()) {
                s1.push(x);
            }else {
                // 先把s1中的所有元素依次弹出放入s2
                while (!s1.isEmpty()) {
//                s2.push(s1.pop());
                    int val = s1.pop();
                    s2.push(val);
                }
                // 将新元素直接放入s1，此时新元素就处在s1的栈底
                s1.push(x);
                // 再次将s2的所有值依次弹出放入s1
                while (!s2.isEmpty()) {
                    s1.push(s2.pop());
                }
            }
        }

        public int pop() {
            return s1.pop();
        }

        public int peek() {
            return s1.peek();
        }

        public boolean empty() {
            return s1.isEmpty();
        }
    }
}
